Technical Aid to the Disabled

Project 98-11245

REV D 3-Nov-1998
Addition of radio remote control to a toy train for a child with cerebal palsy.

(Click on images for higher resolution view)

Transmitter

This is an Oatley Electronics TX2 with the pushbuttons and 12V battery clip removed. A new PCB is fitted which includes a 12V low current regulator and pin headers for the control switches, indicator LED, and power socket.

The design was modified to transmit continuously and to invert the logic sense of the pushbuttons. The completed PCB was then mounted in a small plastic box, with the following external attachments;

A data sheet (Page 1, Page 2) for the encoder and decoder chips was faxed from Kitsrus of Hong Kong.

See also the circuit schematic.

Receiver

This is Oatley Electronic's 318MHz receiver module from their two channel UHF remote control kit, mounted at right angles to a board containing the remote control decoder chip (A5885M, left) and a PIC 12C509 microcontroller (left of centre).

The microcontroller detects the button presses and drives a logic level power MOSFET 2SK2175 (right of centre), which drives the locomotive motor. A 5V regulator (bottom right) provides regulated logic power.

The black area to the right is for power switch clearance.

See also the circuit schematic and the code (final burn to 12c509).

Power

The locomotive tender has a battery compartment for six C size batteries, to which is attached an inline fuse (2A), a power switch, and a pin header socket.

Assembly

The receiver board sits vertically within the rear of the tender, with the indicator LEDs facing upwards. Room is provided on the PCB to allow clearance of the power switch mounted on the side wall.

A pin header socket is attached to the cable to the locomotive, and uses the two outer pins leaving the centre pins free.

Unfortunately, the power socket is not keyed, increasing the risk of reverse polarity connection and subsequent failure.

External Controls

The indicator LEDs are visible through the original switch mounting hole. The LED closest to the power switch is a CPU heartbeat indicator. The other LED lights when the transmitter is active.

Locomotive Interconnect

The cable from the tender to the locomotive required re-sheathing with heat shrink tubing. The plug is marked to indicate the direction it should face when inserted in the locomotive tail.

Final View

That guy must have a sore back by now.

Parts List

How much did it all cost?

Technical Aid to the Disabled                        
Project 98-11245       
Revision AX1           
12th October 1998      

Transmitter

Supplier   Part        Description                     Cost   Qty Price

Jaycar     MP-3002     12V DC 150mA Plugpack          12.95  1.00 12.95
Jaycar     PP-0512     2.5mm ID 5.5mm OD DC Plug       1.30  1.00  1.30
Jaycar     WH-5543     Heatshrink                      1.95  0.16  0.31
Jaycar     PP-0524     2.5mm DC Bulkhead Socket        2.25  1.00  2.25
Jaycar     PS-0123     3.5mm Bulkhead Socket           1.60  2.00  3.20
Stock      N/A         Plastic Box                     4.00  1.00  4.00
Stock      N/A         Veroboard 45mm x 35mm           2.00  1.00  2.00
Stock      N/A         Wire                            0.50  1.00  0.50
Jaycar     HM-3211     Pin Header                      0.05  8.00  0.40
Jaycar     HM-3218     Pin Header Socket, 4 pin        0.65  1.00  0.65
Jaycar     HM-3217     Pin Header Socket, 2 pin        0.50  2.00  1.00
Jaycar     ZR-1004     1N4004 1A 400V Diode            0.08  1.00  0.08
Jaycar     RE-6130     100uF Electrolytic              0.35  1.00  0.35
Jaycar     RZ-6648     10uF Tantalum Capacitor         1.00  1.00  1.00
Jaycar     RC-5348     0.01uF Ceramic Capacitor        0.30  1.00  0.30
Jaycar     ZV-1542     78L12 Voltage Regulator         1.20  1.00  1.20
Jaycar     RR-0596     10k 0.25W Resistor              0.40  2.00  0.80
Oatley     TX2         Keychain Transmitter           15.00  1.00 15.00

                       Transmitter Total                          47.29

Receiver   

Supplier   Part        Description                     Cost   Qty Price

Jaycar     WH-5543     Heatshrink                      1.95  0.16  0.31
Stock      N/A         Push on, Push off switch        1.00  1.00  1.00
Jaycar     SZ-2015     Inline Fuse Holder              1.10  1.00  1.10
Jaycar     SF-2194     2A 3AG Fuse                     0.25  1.00  0.25
Jaycar     HM-3218     Pin Header Socket, 4 pin        0.65  2.00  1.30
Stock      N/A         Veroboard 35mm x 85mm           3.00  1.00  3.00
Stock      N/A         Wire                            0.50  1.00  0.50
Jaycar     RE-6130     100uF Electrolytic              0.35  1.00  0.35
Jaycar     RZ-6648     10uF Tantalum Capacitor         1.00  1.00  1.00
Jaycar     RC-5348     0.01uF Ceramic Capacitor        0.30  1.00  0.30
MicroZed   IC 7805     7805 Voltage Regulator          0.45  1.00  0.45
MicroZed   IC 12C509-4 PIC12C509/04/P 8 pin RISC CPU   3.00  1.00  3.00
Jaycar     RR-0572     1k 0.25W Resistor               0.40  2.00  0.80
Jaycar     ZD-1692     3mm Red LED                     0.13  2.00  0.26
Oatley     2SK2175     2SK2175 TO-220 Logic MOSFET     2.60  1.00  2.60
Jaycar     HM-3211     Pin Header                      0.05  8.00  0.40
Oatley                 318MHz UHF Rx Module           16.00  1.00 16.00
Oatley                 A5885M Decoder Chip             2.00  1.00  2.00
Jaycar     RR-0620     100k 0.25W Resistor             0.40  1.00  0.40
Coles                  Alkaline C Cells                2.23  6.00 13.37

                       Receiver Total                             48.39

                       Project Total                              95.68


20-Oct-1998